JP2009241199A - Surface treatment method and surface treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a sufficient surface treatment effect by causing sufficient bubble collapse even in treating a treated surface made of a convex curved surface in surface treatment using cavitation peening. <P>SOLUTION: The treated surface 3a is treated by impact pressure generated in bubble collapse by collapsing cavitation bubbles by making cavitation jet 4 collide against a colliding part P of a treated article 3 having the treated surface 3a made of the convex curved surface. The narrowest part 5 and an extended part 6 are continuously formed between a flowing regulating plate 2 and the treated surface 3a by arranging the flowing regulating plate 2 facing against the treated surface 3a in the neighborhood of the colliding part P. The bubble collapse is promoted by flowing the cavitation jet 4 after colliding against the colliding part P to the extended part 6 from the narrowest part 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface treatment method and a surface treatment apparatus, and more particularly to a surface treatment method and a surface treatment apparatus for treating a surface to be processed having a convex curved surface using cavitation peening.

  Conventionally, surface treatment using cavitation peening has been performed for the purpose of strengthening the surface of a metal material or a semiconductor material, cleaning, improving residual stress, and the like (see, for example, Patent Documents 1 and 2).

  Cavitation is a phenomenon in which liquid becomes bubbles as a result of the pressure of a liquid such as flowing water being locally reduced and the pressure decreasing to the saturated vapor pressure of the liquid. In many cases, fine bubbles dissolved in water serve as cavitation nuclei and become cavitation bubbles in a high-speed region (low-pressure region) of the jet. The cavitation bubbles generated by the decrease in the pressure of the liquid will collapse due to the influence of the surface tension of the liquid and the like if the pressure of the liquid is increased again due to the decrease in the flow velocity. This bubble collapse occurs in a short time on the order of several microseconds. For this reason, an impact pressure that reaches several hundred to several thousand atmospheres is generated at the time of bubble collapse.

In the surface treatment by cavitation peening, the surface of the object to be treated is strengthened by using the impact pressure generated when the cavitation bubbles collapse. That is, as shown in FIG. 9, a cavitation jet (a jet of liquid such as water containing cavitation bubbles) 80 collides with the surface of the workpiece 81. The cavitation jet 80 after colliding with the workpiece 81 flows along the workpiece surface 81a, and the velocity of the cavitation jet 80 decreases in the process. As a result, the pressure of the cavitation jet 80 increases and bubble collapse occurs. And the to-be-processed surface 81a is strengthened by the impact pressure generated at this time.
Japanese Patent Laid-Open No. 10-76467 Japanese Patent No. 3464682

  By the way, in the surface treatment by cavitation peening, in order to enhance the surface more efficiently, more cavitation bubbles are collapsed in the vicinity of the treated surface of the workpiece, and the impact pressure generated at that time is reduced. It is important to apply more to the surface to be processed.

  However, as shown in FIG. 10, when the processing surface 82a of the workpiece 82 is a convex curved surface and its radius of curvature is small, the velocity of the cavitation jet 80 after colliding with the workpiece 82 is In the vicinity of the surface 82a, it may not be reduced to the extent that bubble collapse occurs.

  For example, when the processing surface 82a is a convex curved surface having a curvature radius smaller than about 5 mm, a part of the cavitation jet 80 after colliding with the processing object 82 does not decrease the flow velocity until the bubble collapse occurs. , It will flow away from the surface 82a. If it does so, bubble collapse will not fully occur, but processing, such as reinforcement of processed surface 82a, will become insufficient. Even in this case, if the processing time is lengthened, the surface 82a to be processed may be sufficiently strengthened, but this causes a reduction in processing efficiency.

  The present invention has been made in view of the above circumstances, and in the surface treatment using cavitation peening, even when a surface to be processed having a convex curved surface is processed, sufficient bubble collapse is generated and sufficient. It is a technical problem to be solved to achieve the surface treatment effect.

  (1) In the surface treatment method according to claim 1, which solves the above problem, a cavitation bubble is collided by colliding a cavitation jet against an object to be processed having a convex curved surface, and an impact generated when the bubble collapses. A method of treating the surface to be treated by pressure, wherein a flow restriction plate facing the surface to be treated is disposed in the vicinity of a collision portion of the object to be treated which the cavitation jet collides with. Between the plate and the surface to be processed, the narrowest flange portion where the distance between the two is the narrowest and the enlarged portion where the distance between both is wider than the narrowest flange portion, in this order, from the upstream side of the cavitation jet It is formed continuously toward the downstream side, and the bubble collapse is promoted by flowing the cavitation jet after colliding with the collision part from the narrowest part to the enlarged part.

  When a cavitation jet collides with a workpiece whose surface to be processed is a convex curved surface, the velocity of the cavitation jet after the collision decreases in the process of flowing along the surface to be processed. However, if the radius of curvature of the surface to be processed, which is a convex curved surface, is small, a part of the cavitation jet may flow away from the surface to be processed without reducing the flow velocity to the extent that bubble collapse occurs. Then, sufficient bubble collapse does not occur.

  In this regard, in the surface treatment method according to the first aspect, the cavitation jet that collides with the collision portion of the workpiece flows from the narrowest portion to the enlarged portion, so that the flow velocity of the cavitation jet decreases and the pressure increases. This encourages the collapse of cavitation bubbles. That is, the bubbles in the cavitation jet surely collapse at the enlarged portion.

  Therefore, according to the surface treatment method of claim 1, even when the surface to be processed is a convex curved surface and the radius of curvature is small, sufficient bubble collapse can occur near the surface to be processed. it can. Therefore, the impact force generated when the bubbles collapse can be sufficiently applied to the surface to be processed, and the surface to be processed can be reliably processed.

  (2) A surface treatment method according to a second aspect is the surface treatment method according to the first aspect, wherein an interval between the flow restricting plate and the workpiece is wider than the narrowest flange portion. The introduction expansion portion is formed on the upstream side of the cavitation jet of the narrowest ridge portion, and the cavitation jet after colliding with the collision portion is guided from the introduction expansion portion to the narrowest ridge portion.

  In this surface treatment method for an object to be processed, it is possible to guide more cavitation jets after colliding with the collision part of the object to be processed from the introduction expansion part to the expansion part through the narrowest flange part.

  (3) A surface treatment method according to a third aspect is the surface treatment method according to any one of the first to second aspects, wherein an interval D between the narrowest flange portion and the surface to be treated and the convex curved surface. In the relationship with the radius of curvature r, the value of r / D is 0.5-5.

  (4) The surface treatment method according to claim 4 is the surface treatment method according to any one of claims 1 to 3, wherein the curvature radius of the convex curved surface is 1 mm to 5 mm.

  According to this surface modification method, the surface treatment effect by cavitation peening can be effectively achieved even on a surface to be processed having a curved surface having a radius of curvature of 1 mm to 5 mm and a large curvature.

  (5) The surface treatment method according to claim 5 is the surface treatment method according to any one of claims 1 to 4, wherein the cavitation jet collides with the normal line of the flow restricting plate and the collision portion. The angle θ formed by the central axis of the jet is 15 to 75 degrees.

  (6) The surface treatment apparatus according to claim 6 that solves the above-described problem causes a cavitation bubble to collide with an object to be processed having a surface to be processed having a convex curved surface to collapse a cavitation bubble, and an impact generated when the bubble collapses An apparatus for treating the surface to be treated by pressure, comprising: an injection nozzle that injects the cavitation jet to collide the cavitation jet with the workpiece; and a collision portion of the workpiece to which the cavitation jet collides. A flow restricting plate disposed near the surface to be processed, and the flow restricting plate has a narrowest distance between the flow restricting plate and the surface to be processed. And an enlarged portion in which the distance between the two is wider than the narrowest ridge, in this order, is formed continuously from the upstream side to the downstream side of the cavitation jet, and collides with the collision portion. Characterized by the said cavitation jet from outermost narrow portion promotes the bubble collapse by flowing into the expansion unit.

  (7) The surface treatment apparatus according to claim 7 is the surface treatment apparatus for an object to be processed according to claim 6, wherein the flow restriction plate is disposed between the flow restriction plate and the object to be treated. An introduction enlarged portion having an interval larger than the narrowest flange portion is formed on the upstream side of the cavitation jet of the narrowest flange portion, and the cavitation jet after colliding with the collision portion is transferred from the introduction enlarged portion to the It is characterized by being guided to a narrow part.

  Therefore, according to the surface treatment method and the surface treatment apparatus of the present invention, even when a surface to be processed having a convex curved surface is processed, sufficient bubble collapse can be generated to achieve a sufficient surface treatment effect. it can.

  Therefore, for example, a sufficient surface treatment effect can be achieved even for a surface to be processed which is a convex curved surface having a radius of curvature of about 5 mm or less.

The surface treatment apparatus of the present invention is
Hereinafter, specific embodiments of the surface treatment method and the surface treatment apparatus of the present invention will be described in detail. In addition, embodiment described is only one Embodiment, The surface treatment method and surface treatment apparatus of this invention are not limited to the following embodiment. The surface treatment method and the surface treatment apparatus of the present invention can be carried out in various forms that have been modified or improved by those skilled in the art without departing from the scope of the present invention.

(Embodiment 1)
The surface treatment apparatus according to the first embodiment shown in FIG. 1 includes an injection nozzle 1 and a flow restriction plate 2. The spray nozzle 1 and the flow restricting plate 2 are immersed in water filled in a processing tank (water tank) (not shown) together with the workpiece 3.

  The injection nozzle 1 injects the cavitation jet 4 with a predetermined pressure aiming at the collision part (collision center part) P of the workpiece 3. The nozzle 1 can be reciprocated in a direction perpendicular to the jet central axis C of the cavitation jet 4 ejected from the ejection nozzle 1 (in the direction perpendicular to the paper surface in FIG. 1) by a nozzle moving device (not shown).

  The flow restricting plate 2 is a flat plate jig made of a metal material such as stainless steel, and is disposed near the collision surface P of the workpiece 3 by a support (not shown) so as to face the processing surface 3a. In the present embodiment, the flow restricting plate 2 is disposed below the collision portion P of the workpiece 3. The flow restricting plate 2 has a flat surface 21 and an end of the flow restricting plate 2 (on the upstream side of the cavitation jet 4 close to the collision portion P of the object to be processed 3) from the object to be processed 3 toward the tip. And a curved surface 22 formed to increase the distance.

  The workpiece 3 is a round bar (column) made of a metal material such as an aluminum alloy and having a radius r. The outer peripheral side surface (cylindrical side surface) of the workpiece 3 is the processing surface 3a. The surface to be processed 3a is formed by a convex curved surface (cylindrical side surface) having a curvature radius r. The workpiece 3 can be rotated in the forward and reverse directions (clockwise and counterclockwise in FIG. 1) around the axis O of the workpiece 3 by a rotation driving device (not shown).

  Between the flow regulating plate 2 and the surface to be treated 3a of the object 3 to be treated, the narrowest flange 5 having the smallest distance between the two (the flow regulating plate 2 and the object to be treated 3) and the narrowest flange having the smallest distance therebetween. An enlarged portion 6 that is wider than 5 is continuously formed in this order from the upstream side to the downstream side of the cavitation jet 4. The narrowest flange portion 5 and the enlarged portion 6 are formed between the flat surface 21 of the flow restricting plate 2 and the processing surface 3 a of the processing object 3.

  Further, between the flow regulating plate 2 and the treated surface 3 a of the workpiece 3, there is an introduction enlarged portion 7 in which the distance between the two (the flow regulating plate 2 and the workpiece 3) is wider than the narrowest flange portion 5. It is formed on the upstream side of the cavitation jet 4 in the narrowest flange 5. Thereby, between the flow restricting plate 2 and the surface 3 a to be processed 3, the introduction expansion portion 7, the narrowest flange portion 5 and the expansion portion 6 are arranged in this order from the upstream side of the cavitation jet 4 to the downstream side. It is formed continuously toward the side.

  The introduction expansion unit 7 includes a first introduction expansion unit 7 a formed between the curved surface 22 of the flow restricting plate 2 and the processing target surface 3 a of the workpiece 3, the flat surface 21 of the flow restricting plate 2, and the processing target. It consists of the 2nd introduction expansion part 7b formed between the to-be-processed surfaces 3a of the thing 3. FIG. The 1st introduction expansion part 7a and the 2nd introduction expansion part 7b are continuously formed from the upstream side of the cavitation jet 4 toward the downstream side in this order.

  Here, the shape and size of the object to be processed 3 are not particularly limited as long as the object 3 has a surface 3a to be processed having a predetermined convex curved surface. The radius of curvature r of the convex curved surface that constitutes the surface to be processed 3a is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. If the radius of curvature r of the convex curved surface constituting the surface to be processed 3a is too small, when the cavitation jet 4 flows from the narrowest flange 5 to the enlarged portion 6, the flow velocity cannot be sufficiently reduced, and the surface to be processed Cavitation collapse near 3a is reduced. On the other hand, if the curvature radius r of the convex curved surface is too large, the increment of the effect by the flow restricting plate 2 becomes small.

  Further, the distance D between the flow restricting plate 2 and the treated surface 3a of the workpiece 3 in the narrowest flange portion 5 (that is, the shortest distance between the flow restricting plate 2 and the treated object 3) D and the treatment target comprising a convex curve In relation to the radius of curvature r of the surface 3a, the value of r / D is preferably 0.5 to 5, and more preferably 1 to 3. If the value of r / D is too small, the flow velocity cannot be sufficiently reduced when the cavitation jet 4 flows from the narrowest ridge portion 5 to the enlarged portion 6. On the other hand, if the value of r / D is too large, the flow rate of the cavitation jet 4 that passes through the narrowest flange 5 becomes insufficient, and as a result, the processing efficiency decreases.

  Furthermore, the angle (inclination angle of the flow restricting plate 2) θ formed by the normal line on the flat surface 21 of the flow restricting plate 2 and the jet central axis C of the cavitation jet 4 before colliding with the collision portion P is 15 degrees or more. It is preferably 75 degrees, more preferably 30 to 60 degrees. If the angle θ is too small, the flow of the cavitation jet 4 before colliding with the collision part P is disturbed by the flow restricting plate 2. When a turbulent flow is generated in the cavitation jet 4 before the collision in the collision part P, the turbulent flow prevents the cavitation jet 4 after the collision from flowing into the enlarged part 6 from the narrowest part 5 to the collision part P. As a result, the amount of the cavitation jet 4 flowing from the narrowest ridge portion 5 to the enlarged portion 6 is reduced, and the processing efficiency is lowered. On the other hand, a part of the cavitation jet 4 after the collision flowing from the collision part P of the workpiece 3 along the treated surface 3a is separated from the treated surface 3a, but if the angle θ is too large, the cavitation jet 4 The amount of peeling increases. As a result, the amount of the cavitation jet 4 flowing from the narrowest ridge portion 5 to the enlarged portion 6 is reduced, and the processing efficiency is lowered. The jet central axis C of the cavitation jet 4 before colliding with the collision part P and the nozzle axis of the injection nozzle 1 coincide.

  A surface treatment method according to this embodiment using the surface treatment apparatus having the above configuration will be described below.

  In the water, the cavitation jet 4 is jetted at a predetermined pressure for a predetermined time, aiming at the collision portion (collision center portion) P from the injection nozzle 1 separated by a distance L from the collision portion P of the workpiece 3. At this time, the cavitation jet 4 may be jetted while rotating the workpiece 3, and the direction perpendicular to the jet central axis C of the cavitation jet 4 jetted from the jet nozzle 1 (the axis of the workpiece 3 The cavitation jet 4 may be jetted while moving the jet nozzle 1 in a direction parallel to O).

  The pressure of the cavitation jet 4 jetted from the jet nozzle 1, the distance L from the jet port of the jet nozzle 1 to the collision part P of the workpiece 3 and the processing time are the treatments for the material of the workpiece 3 and the processing surface 3a. It can be set as appropriate according to the type of the item. For example, when the workpiece 3 is made of an aluminum alloy and is treated for the purpose of strengthening the treated surface 3a, the pressure of the cavitation jet 4 is about 10 MPa to 30 MPa, and the collision of the workpiece 3 from the jet nozzle 1 is performed. The distance L to the portion P can be set to about 10 mm to 50 mm mm, and the processing time per 1 mm length of the workpiece 3 can be set to about 5 seconds to 30 seconds.

  When the cavitation jet 4 collides with the workpiece 3 having the convex surface 3a to be processed, the cavitation jet 4 after the collision reduces the flow velocity in the process of flowing along the processed surface 3a. However, if the radius of curvature r of the processing surface 3a made of a convex curved surface is small, a part of the cavitation jet 4 flows away from the processing surface 3a without reducing the flow velocity to the extent that bubble collapse occurs. There is a case. Then, sufficient bubble collapse does not occur.

  In this regard, in the surface treatment method according to the present embodiment, most of the cavitation jet 4 after colliding with the collision part P of the workpiece 3 flows from the introduction expansion part 7 through the narrowest flange part 5 to the expansion part 6. . The cavitation jet 4 greatly reduces the flow velocity when flowing from the narrowest ridge portion 5 to the enlarged portion 6. For this reason, the pressure of the cavitation jet 4 greatly increases in the enlarged portion 6, and sufficient collapse of the cavitation bubbles occurs.

  Therefore, according to the surface treatment method according to the present embodiment, sufficient bubble collapse occurs in the vicinity of the surface to be processed 3a even when the surface to be processed 3a is a convex curved surface and the radius of curvature r is small. be able to. Therefore, the impact force generated when the bubble collapses can be sufficiently applied to the surface to be processed 3a in the vicinity of the enlarged portion 5, and the surface to be processed 3a can be reliably processed.

  In particular, in the present embodiment, since the introduction expansion portion 7 is provided on the upstream side of the narrowest flange portion 5, more cavitation jets 4 after colliding with the collision portion P of the workpiece 3 are guided to the introduction expansion portion 7. be able to. For this reason, since the flow rate of the cavitation jet 4 supplied from the narrowest flange portion 5 to the enlarged portion 6 is increased, it is possible to improve the processing efficiency.

(Embodiment 2)
In the surface treatment apparatus according to the second embodiment shown in FIG. 2, the shape of the flow restricting plate 2 in the first embodiment is changed.

  That is, the flow restricting plate 2 in the surface treatment apparatus according to the second embodiment has a concave curved surface 23 that is concave toward the workpiece 3 instead of the curved surface 22.

  Other configurations of the surface treatment apparatus according to the second embodiment are the same as those of the first embodiment. Therefore, by performing the same surface treatment method as that of the first embodiment, the same effects as those of the first embodiment can be obtained.

(Embodiment 3)
In the surface treatment apparatus according to the third embodiment shown in FIG. 3, the shape of the flow restricting plate 2 in the first embodiment is changed.

  That is, the flow restricting plate 2 in the surface treatment apparatus according to the third embodiment does not have the curved surface 22 but has only the flat surface 21.

  The other configuration of the surface treatment apparatus according to the third embodiment is the same as that of the first embodiment. Therefore, by performing the same surface treatment method as that of the first embodiment, substantially the same effects as those of the first embodiment can be obtained.

  In the surface treatment apparatus according to the third embodiment, since the introduction expansion unit 7 is not provided on the upstream side of the narrowest flange portion 5, the cavitation jet 4 after colliding with the collision portion P of the workpiece 3 is narrowed down. The amount that can be supplied from the unit 5 to the enlarged unit 6 is reduced as compared with the first embodiment.

(Embodiment 4)
In the surface treatment apparatus according to the fourth embodiment shown in FIG. 4, the shape of the flow restricting plate 2 in the first embodiment is changed.

  That is, the flow restricting plate 2 in the surface treatment apparatus according to the fourth embodiment is disposed on one end side of the flow restricting plate 2 (upstream side of the cavitation jet 4 close to the collision portion P of the workpiece 3) instead of the curved surface 22. The inclined surface 24 is formed so that the distance from the workpiece 3 becomes longer toward the tip.

  The other configuration of the surface treatment apparatus according to the fourth embodiment is the same as that of the first embodiment. Therefore, by performing the same surface treatment method as that of the first embodiment, the same effects as those of the first embodiment can be obtained.

(Other embodiments)
Although Embodiment 1-4 demonstrated the example which arrange | positions the one flow control board 2 below the collision part P of the to-be-processed object 3, For example, the flow control board 2 is each below and upper than the collision part P, for example. May be arranged.

  In the first to fourth embodiments, the example in which the cavitation jet 4 collides with the collision portion P on the side of the workpiece 3 from the horizontal direction has been described. The cavitation jet 4 may collide from the direction.

  Furthermore, the shapes of the surface 3a to be processed and the flow restriction plate 2 are not limited to those described in the first to fourth embodiments. For example, the processed surface 3a may be a hemispherical or bowl-shaped convex curved surface, and in this case, the flow regulating plate 2 having a shape corresponding to the hemispherical or bowl-shaped convex curved surface can be used.

  In addition, although the example which uses water for a jet flow was demonstrated in Embodiment 1-4, you may use oil, an emulsion (emulsion), and another liquid, without being limited to this.

Example 1
Using the surface treatment apparatus shown in FIG. 1 described in Embodiment 1, surface treatment was performed under the following conditions.

Object to be treated 3: φ6 mm round bar made of aluminum alloy Curvature radius of surface to be treated 3a: r = 3 mm
Distance between the flow restricting plate 2 and the processing surface 3a of the processing object 3 in the narrowest flange 5: D = 2 mm
Relationship between the distance D and the radius of curvature r: r / D = 1.5
Angle formed between the normal line on the flat surface 21 of the flow restricting plate 2 and the jet central axis C of the cavitation jet 4 before colliding with the collision part P: θ = 45 degrees Nozzle diameter of the jet nozzle 1: φ1 mm
Pressure of cavitation jet 4: 10 MPa
Distance from the injection port of the injection nozzle 1 to the collision part P of the workpiece 3: L = 23 mm
Processing time: 30 minutes Rotation of workpiece 3: None Movement of injection nozzle 1: None (Example 2)
Surface treatment was performed under the same conditions as in Example 1 using the surface treatment apparatus shown in FIG.

(Example 3)
Using the surface treatment apparatus shown in FIG. 1 described in the first embodiment, the workpiece 3 is rotated around the axis O (counterclockwise in FIG. 1) under the following conditions, and the spray nozzle 1 is moved to the workpiece 3. Surface treatment was performed under the same conditions as in Example 1 except that the film was moved in the direction of the axis O.

Rotation speed of workpiece 3: 3 rpm
Movement speed of the injection nozzle 1: 6 mm / min (Example 4)
Using the surface treatment apparatus shown in FIG. 3 described in Embodiment 3, surface treatment was performed under the same conditions as in Example 1.

(Example 5)
Using the surface treatment apparatus shown in FIG. 4 described in Embodiment 4, surface treatment was performed under the same conditions as in Example 1.

(Example 6)
Using the surface treatment apparatus shown in FIG. 1 described in the first embodiment, the workpiece 3 is rotated around the axis O (clockwise in FIG. 1 which is the opposite direction to that of the third embodiment) and sprayed under the following conditions. Surface treatment was performed under the same conditions as in Example 1 except that the nozzle 1 was moved in the direction of the axis O of the workpiece 3.

Rotation speed of workpiece 3: 3 rpm
Movement speed of injection nozzle 1: 6 mm / min (Example 7)
Using the surface treatment apparatus shown in FIG. 4 described in the fourth embodiment, the workpiece 3 is rotated around the axis O (counterclockwise in FIG. 4) under the following conditions, and the spray nozzle 1 is moved to the workpiece 3. Surface treatment was performed under the same conditions as in Example 1 except that the film was moved in the direction of the axis O.

Rotation speed of workpiece 3: 3 rpm
Movement speed of injection nozzle 1: 6 mm / min (Example 8)
Using the surface treatment apparatus shown in FIG. 4 described in the fourth embodiment, the workpiece 3 is rotated around the axis O (clockwise in FIG. 4 which is the opposite direction to that of the seventh embodiment) and sprayed under the following conditions. Surface treatment was performed under the same conditions as in Example 1 except that the nozzle 1 was moved in the direction of the axis O of the workpiece 3.

Rotation speed of workpiece 3: 3 rpm
Movement speed of injection nozzle 1: 6 mm / min (Comparative Example 1)
Surface treatment was performed under the same conditions as in Example 1 except that the flow restricting plate 2 was not provided.

(Comparative Example 2)
Surface treatment was performed under the same conditions as in Example 3 except that the flow restricting plate 2 was not provided.

(Comparative Example 3)
In the surface treatment apparatus shown in FIG. 3 described in the third embodiment, the flow restricting plate 2 is directly below the workpiece 3 and the jet axis C of the cavitation jet 4 injected from the injection nozzle 1 and the flow restricting plate 2 Except that the angle θ formed by the normal line of the flat surface 21 is 90 degrees and that the cavitation jet 4 is jetted from the jet nozzle 1 aiming at the narrowest flange 5 instead of the workpiece 3. Surface treatment was performed under the same conditions as in Example 1 (see FIG. 5).

  The distance from the injection port of the injection nozzle 1 to the narrowest flange portion 5 was set to L = 23 mm.

(Comparative Example 4)
In the surface treatment apparatus shown in FIG. 4 described in the fourth embodiment, the flow restricting plate 2 is directly below the workpiece 3 and the flow axis C of the cavitation jet 4 injected from the injection nozzle 1 and the flow restricting plate 2 Except that the angle θ formed by the normal line of the flat surface 21 is 90 degrees and that the cavitation jet 4 is jetted from the jet nozzle 1 aiming at the narrowest flange 5 instead of the workpiece 3. Surface treatment was performed under the same conditions as in Example 1 (see FIG. 6).

  The distance from the injection port of the injection nozzle 1 to the narrowest flange portion 5 was set to L = 23 mm.

(Evaluation of processing area)
In Examples 1, 2, 4, and 5 and Comparative Examples 1, 3, and 4, the area of the erosion region (the region in which the surface is damaged and broken by cavitation collapse) on the surface 3a after the surface treatment Was measured. The result is shown in FIG. The horizontal axis of FIG. 7 indicates an index with the area (processing area) of the erosion region of Comparative Example 1 as 100.

  In Comparative Example 1, erosion marks due to cavitation collapse (collapse of cavitation bubbles contained in the cavitation jet 4) were observed only in the vicinity of the collision portion P where the cavitation jet 4 collided with the workpiece 3.

  In Comparative Examples 3 and 4, erosion marks due to cavitation collapse were observed only in the vicinity of the enlarged portion 6. Moreover, the processing area in Comparative Examples 3 and 4 was as small as about half of the processing area in Comparative Example 1. This is because there is no decrease in the flow velocity of the cavitation jet 4 due to the collision with the workpiece 3, and therefore, the flow velocity of the cavitation jet 4 compared to Comparative Example 1 and Example 1 in which the cavitation jet 4 collides with the workpiece 3. Decrease is reduced. As a result, it is considered that the amount of cavitation collapse near the surface to be processed 3a is reduced.

  On the other hand, in Examples 1, 2, 4 and 5, erosion marks due to cavitation collapse were observed in the vicinity of the collision portion P where the cavitation jet 4 collided with the workpiece 3 and in the vicinity of the enlarged portion 6.

  Moreover, the processing area in Examples 1, 2, 4, and 5 became 1.5 times or more of the processing area in the comparative example 1.

  In particular, in Examples 2 and 5, it was possible to supply more cavitation jets 4 after colliding with the collision part P of the workpiece 3 from the narrowest flange part 5 to the enlarged part 6, so in Examples 2 and 5 The processing area in the vicinity of the enlarged portion 6 was larger than the processing area in the vicinity of the enlarged portion 6 in Examples 1 and 4.

(Evaluation of residual stress)
In Examples 3, 6, 7 and 8, and Comparative Example 2, the residual stress of the surface to be processed 3a was measured on the surface to be processed 3a after the surface treatment using an X-ray residual stress measuring device. The result is shown in FIG.

  In Comparative Example 2, a compressive residual stress of about 50 MPa was generated on the entire surface 3a (the entire outer peripheral surface of the round bar) of the object 3 to be processed.

  On the other hand, in Examples 3, 6, 7 and 8, since cavitation collapse was reliably generated in the vicinity of the enlarged portion 6, a compressive residual stress of about 80 MPa larger than the compressive residual stress in Comparative Example 2 was obtained. It occurred on the entire surface 3a of the object 3 to be processed.

  In particular, in Examples 7 and 8, it was possible to generate more cavitation collapse than in Examples 3 and 6, so that a compressive residual stress of about 90 MPa larger than the compressive residual stress in Examples 3 and 6 was applied. It occurred on the entire surface 3a of the processed object 3.

  In addition, depending on the difference in the rotation direction of the workpiece 3, no significant difference was observed in the processing effect.

It is a figure which shows typically the principal part of the surface treatment apparatus which concerns on Embodiment 1 while describing the surface treatment method which concerns on Embodiment 1 typically. It is a figure which shows typically the principal part of the surface treatment apparatus which concerns on Embodiment 1 while describing the surface treatment method which concerns on Embodiment 2 typically. It is a figure which shows typically the principal part of the surface treatment apparatus which concerns on Embodiment 1 while describing the surface treatment method which concerns on Embodiment 3 typically. It is a figure which shows typically the principal part of the surface treatment apparatus which concerns on Embodiment 1 while describing the surface treatment method which concerns on Embodiment 4 typically. It is a figure which shows typically the principal part of the surface treatment apparatus which concerns on the comparative example 3, while explaining the surface treatment method which concerns on the comparative example 3. FIG. It is a figure which shows typically the principal part of the surface treatment apparatus which concerns on the comparative example 4 while explaining the surface treatment method which concerns on the comparative example 4. FIG. In Examples 1, 2, 4, and 5 and Comparative Examples 1, 3, and 4, it is a figure which shows the result of having measured the area (processed area) of the erosion area | region about the to-be-processed surface after surface treatment. In Example 3, 6, 7, and 8 and the comparative example 2, it is a figure which shows the result of having measured the residual stress about the to-be-processed surface after surface treatment. It is a figure which illustrates typically the surface treatment method using the conventional cavitation peening. It is a figure which illustrates typically the surface treatment method using other conventional cavitation peening.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Injection nozzle 2 ... Flow control board 3 ... To-be-processed object 3a ... To-be-processed surface 4 ... Cavitation jet 5 ... The narrowest narrow part 6 ... Expansion part 7 ... Introduction expansion part

Claims (7)

Cavitation jet collides with an object having a surface to be processed having a convex curved surface to collapse cavitation bubbles, and the surface to be processed is processed by an impact pressure generated at the time of bubble collapse,
By disposing a flow restricting plate facing the surface to be processed in the vicinity of the collision portion of the object to be processed with which the cavitation jet collides, a gap between both is provided between the flow restricting plate and the surface to be processed. The narrowest narrow part and the enlarged part in which the distance between the two is wider than the narrowest narrow part, in this order, continuously from the upstream side to the downstream side of the cavitation jet,
The surface treatment method according to claim 1, wherein the bubble collapse is promoted by flowing the cavitation jet after colliding with the colliding portion from the narrowest narrow portion to the enlarged portion. Between the flow restricting plate and the object to be processed, an introduction expansion part in which the distance between the two is wider than the narrowest narrow part is formed on the upstream side of the cavitation jet of the narrowest narrow part,
The surface treatment method according to claim 1, wherein the cavitation jet after colliding with the collision part is guided from the introduction enlarged part to the narrowest narrow part.   The value of r / D is 0.5-5 in the relationship between the space | interval D of the said narrowest flange part and the said to-be-processed surface, and the curvature radius r of the said convex curved surface. The surface treatment method as described in any one of these.   The surface treatment method according to claim 1, wherein a radius of curvature of the convex curved surface is 1 mm to 5 mm.   5. The angle θ formed by the normal line of the flow restricting plate and the jet central axis of the cavitation jet colliding with the collision portion is 15 to 75 degrees. The surface treatment method as described in one. A device for collapsing a cavitation jet against a workpiece having a surface to be processed having a convex curved surface to collapse a cavitation bubble, and processing the surface to be processed by an impact pressure generated at the time of bubble collapse,
An injection nozzle that injects the cavitation jet to cause the cavitation jet to collide with the workpiece;
A flow restriction plate disposed in the vicinity of a collision portion of the workpiece to which the cavitation jet collides, and disposed to face the treatment surface,
The flow restricting plate includes, in this order, a narrowest flange portion having a narrowest interval between the flow restricting plate and the surface to be processed, and an enlarged portion in which the interval between the two is wider than the narrowest flange portion. The cavitation jet is continuously formed from the upstream side to the downstream side, and the bubble collapse is promoted by flowing the cavitation jet after colliding with the collision part from the narrowest part to the enlarged part. The surface treatment apparatus characterized by the above-mentioned.   The flow restricting plate is formed between the flow restricting plate and the object to be processed on the upstream side of the cavitation jet of the narrowest ridge, with an interval between the two being wider than the narrowest ridge. The surface treatment apparatus according to claim 6, wherein the cavitation jet after colliding with the collision portion is guided from the introduction enlarged portion to the narrowest narrow portion.

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